On their website, craterchains and his group ask questions like "Where did the companion mountain to Arsai [sic] Mons go?" in reference to the Viking mosaic he posted. The duplicate Arsia Mons is a painfully obvious error from hand-mosaicking of low resolution Viking images with poor or no cartographic control. This is the level of rigor involved in all of the investigations I have seen him present. Take it with all the seriousness it deserves.

Edit: The mosaic they call Viking from 1976 at the top of the thread is in fact Mariner from 1971 - the poor cartographic control is even less surprising. I should have realized.

Edit2: My edit stands corrected (by craterchains' post below). Viking mosaic after all. My other comments remain.

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“The simplest schoolboy is now familiar with truths for which Archimedes would have sacrificed his life.” – Earnest Renan